Anticoagulation therapy involves the use of certain medications to prevent blood clots from forming in the circulatory system. If a blood clot forms in a vein or artery, it can travel to the heart, brain or lungs, causing, depending on the clot's location, a heart attack, stroke or pulmonary embolism. People who have irregular heart rhythms (atrial fibrillation) or congenital heart defects, or who have had coronary stents inserted or undergone heart-valve surgery, have a greater likelihood of getting blood clots.
Anticoagulant drugs interrupt the chemical processes involved in blood clotting to extend the time it takes blood clots to form. Anticoagulants can only prevent clots from forming; they are not capable of breaking up ones that have already formed. Heparin and warfarin are two types of anticoagulants; heparin is sometimes started intravenously. Anticoagulant drugs are considered a more aggressive treatment than antiplatelet drugs, which are designed to "thin" the blood. Anticoagulants are usually recommended for people at high risk for strokes, or who have atrial fibrillation. In the past few years, the United States Food and Drug Administration has approved a number of new anticoagulants: apixaban, dabigitran and rivaroxaban.
Anticoagulation Therapy Testing
To determine the correct dosage of anticoagulant, careful monitoring of a patient's blood-clotting times is essential. Monthly or weekly laboratory testing is usually performed to determine that a patient's International Normalized Ratio (INR) is within a safe range. An INR that is higher than the target range indicates a higher risk of bleeding, while an INR that is lower than the target range indicates a higher risk of developing a clot. Depending on INR, a patient's anticoagulant dose may be adjusted.
Risks of Anticoagulation Therapy
Bleeding is the most common risk of anticoagulation therapy. A patient taking anticoagulants must confer with her or his physician before using other medications, including many over-the-counter drugs. Aspirin in particular is known to increase the effect of anticoagulants, which puts the patient at a greater risk for excessive bleeding. Other medications, such as nonsteroidal anti-inflammatories, some medicines used to treat colds or stomach upset, and various herbal formulations and vitamins (particularly vitamin K), may be contraindicated, because they, too, can cause bleeding.
Other risks of anticoagulation therapy include the following:
- Hair loss
- Itchy feet
- Toe pain
Because anyone on anticoagulants is susceptible to internal bleeding, a forceful bump or fall is cause for concern, and a physician should be contacted.